Pertechnetate Scintigraphy for Warthin Tumors of the Parotid Gland: Comparison of Histopathological and Magnetic Resonance Imaging findings

Purpose: To examine the relationships between degrees of Tc pertechnetate (TcO4 ) uptake after acid stimulation and the tumor size as well as histopathological subtypes of Warthin tumor and to evaluate the diagnostic accuracy of TcO4 − scintigraphy and routine magnetic resonance (MR) imaging in differentiating Warthin and non-Warthin tumors of the parotid gland. Methods: We reviewed a total of 83 pathologically proven parotid gland tumors in 79 patients (37 Warthin tumors and 46 non-Warthin tumors) that had been resected after TcO4 − scintigraphy with acid stimulation. Of these, MR imaging was performed in 53 patients before surgery (21 Warthin tumors and 33 non-Warthin tumors), among which contrastenhanced dynamic MR imaging was also performed in 50 patients (20 Warthin tumors and 30 non-Warthin tumors). The Kruskal–Wallis test was used to compare visually scored degrees of TcO4 − uptake with tumor size and histopathological subtypes (epithelial components of 70%–80%, 40%–60%, and 20%–30%) in 37 Warthin tumors. The findings of T2-weighted and contrast-enhanced dynamic MR imaging were evaluated for the differential diagnosis of Warthin and non-Warthin tumors. We used the proportional test to compare the accuracy of TcO4 − scintigraphy, T2-weighted MR imaging, and contrast-enhanced dynamic MR imaging in diagnosing Warthin tumor. Results: TcO4 − uptake in Warthin tumors showed marginal but statistically insignificant associations with tumor size (P = 0.092) and tumor pathological subtype (P = 0.070). Of the 8 false-negative tumors, 6 contained 1 or more of the following changes: hemorrhage, hyaline or cystic degeneration, fibrosis, and infarction. A metastatic atypical meningioma showed false-positive uptake. The diagnostic accuracy was 89% for scintigraphy (sensitivity, 78%; specificity, 98%), 81% for T2weighted MR imaging (sensitivity, 81%; specificity, 82%), and 82% for contrast-enhanced dynamic MR imaging (sensitivity, 60%; specificity, 97%); significant differences in the diagnostic accuracy among the modalities were absent (P = 0.37). Conclusions: TcO4 − uptake in Warthin tumors does not appear to depend solely on the tumor size or histological subtype and may be affected by nonviable parenchymal changes in the tumors. Scintigraphy may be equal to T2-weighted and contrast-enhanced dynamic MR imaging in differentiating Warthin and non-Warthin tumors.